System, apparatus, and methods for proactive allocation of wireless communication resources

ABSTRACT

A system for communication between a mobile node and a communications network is provided for use with a communications network having one or more communications network nodes that define a foreign agents and that communicate with the mobile node in a predefined region. The system includes a ghost-foreign agent that advertises a foreign agent so that the mobile node is aware of the foreign agent when the mobile node is located outside the predefined region. The system further includes a ghost-mobile node that signals the foreign agent in response to the foreign agent advertising and based upon a predicted future state of the mobile node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/491,436, filed in the United States Patent and Trademark Office onJuly 31, 2003, the entirety of which is incorporated herein byreference.

BACKGROUND

1. Field of the Invention

This invention relates to the field of communications, and, moreparticularly, to allocation of resources of a communications network forsupporting wireless communications.

2. Description of the Related Art

Mobile communications broadly encompass the various devices andtechniques that enable individuals to communicate without having to relyon a static network infrastructure. Laptop computers, palmtops, personaldigital assistants (PDAs), and cellular phones are all part of thegrowing array of computing and telephony-based mobile devices that canbe used to exchange voice signals and digitally encoded data from remotelocations. The general architecture for mobile systems entails mobilenodes, or hosts, communicating with one another through a series of basestations that serve distinct zones or cells. According to thisarchitecture, a mobile node remains in contact with a communicationnetwork by repeatedly tearing down old connections and establishing newconnections with a new base station as the host moves from one cell toanother.

What is generally needed for such architectures to function adequatelyis some way for the mobile node to let other nodes know where the mobilenode can be reached while the host is moving or located away from home.In accordance with a typical mobile networking protocol, a mobile noderegisters with a home agent so that the home agent can remain a contactpoint for other nodes that wish to exchange messages or otherwisecommunicate with the mobile node as it moves from one location toanother. An example of such a protocol is Mobile Internet Protocol(Mobile IP). Mobile IP allows a mobile node to use two IP addresses, onebeing a fixed home address and the other being a care-of address. Thecare-of address changes as the mobile node moves between networksthereby changing its point of attachment to a network. When the mobilenode links to a network other than one in which the home agent resides,the mobile node is said to have linked to a foreign network. The homenetwork provides the mobile node with an IP address and once the nodemoves to a foreign network and establishes a point of attachment, themobile node receives a care-of address assigned by the foreign network.

Mobile IPv.4 depends on the interaction between a home agent and foreignagents, the foreign agents serving as wireless access points distributedthroughout a coverage area of a network or an interconnection ofmultiple networks. This architecture, however, does have disadvantages.These have led to assorted proposals for enhancing the capabilities ofMobile IP. One such proposal is to use a hierarchy of foreign agentsintended to reduce the number of registrations required for the mobilenode.

FIG. 1 is a schematic diagram illustrating an exemplary architecture fora mobile communications system 100 using hierarchical foreign agents asis known in the art. As shown, the system 100 can include a home agent105 and a foreign agent 110, each communicatively linked via acommunications network 115 such as the Internet. The foreign agent 110further is communicatively linked with the hierarchy of foreign agents120, 125, 130, 135, 140, and 145. Accordingly, a mobile host 150 canchoose a foreign agent which is closer than the others as a registrationpoint. Registration messages are constrained to that region only.

The mobile node 150 travels in range of foreign agent 145. The mobilenode 150 registers with foreign agent 145, foreign agent 125, andforeign agent 110 as the mobile node's 150 care-of addresses. Aregistration request also reaches the home agent 105. The registrationreply reaches the mobile node 150 via the reverse path. Accordingly,packets received at the home agent 105 that are to be routed to themobile node 150 can be tunneled to foreign agent 110, which tunnels thepackets to foreign agent 125, and finally to foreign agent 145 prior totransmitting the packets to the mobile node 150.

Nevertheless, registration delays and associated information losses canstill represent significant obstacles for wireless communicationsinvolving a mobile node. This stems mainly from the inevitable delayassociated with the setting up of a new communication link each time themobile node is handed off from one foreign agent to another. The setuprequires time for the network to negotiate protocol details, establishcommunication rates, and decide the applicable error-handling approachesto be employed. These should each be resolved as a prelude toestablishing the actual connection for the exchange of data. Withconventional systems and devices, the setting up typically must awaitthe arrival of the mobile node in the predefined region of coverage forthe foreign agent to which the mobile node is to be handed off.Depending upon the mobile network configuration, the time required forregistration can rival the time in which the mobile node dwells within agiven cell coverage area. Moreover, data packets may be lost if theyarrive for the mobile node during the time in which the setup is beingworked out.

SUMMARY OF THE INVENTION

The present invention provides a preemptive and predictive solution forcommunications in wireless communications networks. More particularly,the present invention provides two different types of ghost-entitiesthat can be used individually or jointly in setting up a wirelessconnection between a mobile node and a foreign agent. The ghost entitiescan act on behalf of a wireless node and a foreign agent. They candetermine and use predicted information to improve the performance ofwireless communications, especially those involving a mobile node movingat moderate or high speeds. As explained herein, the ghost entitiescause communication network resources to be allocated proactively ratherthan reactively.

One aspect of the present invention pertains to a wireless node pair formobile wireless communications. The wireless network node can include amobile node and a ghost-mobile node. The ghost-mobile node can beconfigured to register the mobile node and allocate resources forcommunicating with the mobile node according to a predicted future stateof the mobile node. Notably, the ghost-mobile node can be instantiatedin at least one additional wireless network node proximate to thepredicted future location of the mobile node. Additionally, theghost-mobile node can be configured to predict the future location ofthe mobile node. The ghost-mobile node also can buffer data packetsintended for the mobile node and sent by a correspondent node.

Another aspect of the present invention includes a network node pairthat includes a foreign agent and a ghost-foreign agent. Theghost-foreign agent can be configured to provide an advance notificationto the mobile node of a presence of a next wireless network nodeproximate to the predicted future location of the mobile node. Inparticular, a ghost-foreign agent corresponding to a second foreignagent can make the mobile node aware of the presence of the secondforeign agent by signaling an advertisement to the mobile node from afirst foreign agent.

Another aspect of the present invention can include a method of mobilecommunications. The method can include estimating a future location of amobile node, sending a notification to the mobile node indicating apresence of a next foreign agent proximate to the estimated futurelocation of the mobile node, and registering the next wireless networknode as the care-of-address to be used to communicate with the mobilenode.

BRIEF DESCRIPTION OF THE DRAWINGS

There are shown in the drawings, embodiments which are presentlypreferred, it being understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown.

FIG. 1 is a schematic diagram illustrating an exemplary system formobile communications that incorporates hierarchical foreign agents asknown in the art.

FIGS. 2A and 2B are schematic diagrams illustrating a method ofoperation for an exemplary system for mobile communications inaccordance with the inventive arrangements disclosed herein.

FIG. 2C is a schematic diagram illustrating another exemplary networkarchitecture where a foreign agent is surrounded by a plurality of otherforeign agents.

FIG. 3 is a schematic diagram illustrating a message structure that canbe assembled for the home agent and/or foreign agent by the ghost-mobilenode in accordance with one embodiment of the inventive arrangementsdisclosed herein.

FIG. 4 is a schematic diagram illustrating a data packet that can beformulated and sent by the ghost-foreign agent in accordance with oneembodiment of the inventive arrangements disclosed herein.

FIG. 5 provides a flowchart illustrative of a method aspect of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a system, apparatus, and methods forreducing delays and information losses in a single wirelesscommunication network or interconnection of multiple communicationnetworks. The system, apparatus, and methods of the present invention,more specifically, reduce registration overhead and setup timesassociated with mobile node handoffs. The system, apparatus, and methodsalso reduce or eliminate losses due to dropped data packets. Theadvantageous results are achieved by causing communication networkresources to be allocated proactively rather than reactively.

More particularly, the present invention provides a ghost-mobile nodeand a ghost-foreign agent. The ghost-mobile node can serve as a virtualrepeater capable of registering and allocating communication resourcesby predicting where the mobile node's next handoff will occur as themobile node moves relative to the communication network's nodes,including those edge nodes that define foreign agents. Time delays andinformation losses also can be reduced by the ghost-foreign agent. Theghost-foreign advertises the foreign agent's presence in thecommunication network using a neighboring foreign agent. Theghost-foreign agent can thus make a mobile node aware of a correspondingforeign agent's presence in a communication network before the mobilenode actually arrives in the physical region covered by the foreignagent.

Accordingly, the ghost-mobile node and the ghost-foreign agent,operating either individually or jointly, can cause networkcommunication resources to be allocated preemptively rather thanpassively as in conventional communications networks in which handoffstypically only follow an exchange of setup information following amobile node's arrival in the physical region covered by the foreignagent. The ghost-mobile node and ghost-foreign agent can also serve to“hide” handoff operations from network layers, thereby hiding operationsthat would otherwise tend to reduce system performance.

FIGS. 2A and 2B are schematic diagrams illustrating an exemplaryinterconnection of communication networks 200, including one home and aplurality of foreign networks, that facilitate wireless communicationinvolving at least one mobile host in accordance with the inventivearrangements disclosed herein. As shown in FIGS. 2A and 2B, theinterconnected communication networks 200 can include a wireless nodepair 202, described in more detail below, as well as two network nodepairs 204 a, 204 b that are also described more fully below. Theinterconnection of communication networks 200 also illustrativelyincludes a network node that defines a home agent 205 and anothernetwork node that defines a foreign agent 210.

Each of the network node pairs 204 a, 204 b also includes a networknode, each defining a foreign agent 215, 230. More particularly, thesetwo foreign agents 215, 230 can be identified as leaf foreign agents toemphasize the hierarchical tree structure of the network nodes, in whichthe home agent 205 serves as the root, one foreign agent 210 serves asan intermediate branch, and the other two foreign agents serve asleaves. Illustratively, the interconnection of communication networks200 further includes a mobile node 250.

As will be readily understood by those of ordinary skill in the art, theterm node is used herein to denote any addressable device that connectsto a communication network and that can recognize, process, or forwarddata or other communication transmissions. Therefore, each of thenetwork nodes defining the foreign agents 210, 215, 230 can be generalpurpose computers on which is running specialized routing software, oralternately, application-specific devices such as routers for relayingcommunication transmissions. Indeed, as will be readily appreciated bythose of ordinary skill in the art, the network nodes can be implementedwith any information processing systems having the ability tocommunicate with one another via suitable wired and/or wirelesscommunications links. Moreover, those of ordinary skill in the art willalso recognize that the interconnection of networks 200 can includeadditional foreign agents as needed to create an interconnection ofnetworks of any size and configuration. The interconnection of networks200 itself can comprise a single network comprising a plurality ofinterconnected nodes.

The mobile node 250, as part of normal use, changes its point ofattachment to the networks forming the interconnection of networks 200.The mobile node 250 can be a computing device having suitableoperational software and a wireless transceiver. Accordingly, the mobilenode 25l can engage in two-way wireless communications with thecommunication network edge nodes, defining leaf foreign agents or simplyforeign agents 215, 230. The mobile node 250, for example, can beimplemented as a standalone portable computing system, or it can be adevice embedded within a larger system such as an automobile, a train,or another form of transportation. The mobile node 250 alternately canbe, for example, a mobile or laptop computer, a hand-held personaldigital assistant (PDA), a cellular phone, or similar device for thewireless exchange of data and/or other communications with theinterconnected networks 200.

The home agent 205 is a network node belonging to the network that isdesignated as the home network. The network is a home network in thesense that it serves as a virtual permanent residence at which themobile node 250 can receive communications from other network nodes,designated as correspondent nodes. By providing an addressable home, thehome agent effectively allows the mobile node 250 to be reachable at itshome address even when the mobile node 250 is not attached to the homenetwork. This is done in a manner analogous to the forwarding of mail toan out-of-town resident or call forwarding a telephone communicationfrom a fixed to a mobile number. According to one embodiment of thepresent invention, the home agent 205 can be implemented as a softwarecomponent executing on a suitable computing system, such as a server orother computing device. The home agent 205 can be communicatively linkedwith a network such as the Internet, thereby enabling two-waycommunications between the home agent 205 and a foreign agent 210.

The foreign agents 210, 215, 230 exist foreign networks in so far asthey are part of networks to which the mobile node 250 iscommunicatively linked when the mobile node 250 is not linked directlywith its home network. Even when the mobile node 250 is not directlylinked with its home network, though, it can receive communications.These communications are typically in the form of datagrams having anappropriate care-of address, as will be readily understood by those ofordinary skill in the art. Accordingly, the foreign agents 210, 215, 230assist the mobile node 250 in receiving datagrams delivered to thecare-of address.

In order for the network nodes to relay datagrams to the mobile node 250when the mobile node is in a foreign network, the mobile node must becommunicatively linked to a foreign agent 215, 230 corresponding to thatparticular foreign network. As the mobile node 250 moves from oneforeign network to another, a handoff is required from the foreign agent215 of the foreign network the mobile node is leaving to the foreignagent 230 of the foreign network at which the mobile node is arriving.The handoff typically entails the mobile node 250 signaling the nextforeign agent 230, requesting registration. Registration typicallyprecedes an updating of the care-of address and an appropriatereallocation of communication network resources so that communicationsaddressed to the home agent can be properly relayed to the mobile node250 by “tunneling” messages through a different set of hierarchicallyarranged network nodes.

As used herein, tunneling refers to the transmission of data intendedfor use only within a private, such as a corporate, network through apublic network wherein the transmission is performed in such a way thatthe routing nodes in the public network are unaware that thetransmission is part of a private network. Tunneling is generallyperformed by encapsulating the private network data and protocolinformation within the public network transmission units so that theprivate network protocol information appears to the public network asdata. Tunneling allows the use of the Internet, which is a publicnetwork, to convey data on behalf of a private network. Common examplesof tunneling techniques can include, but are not limited to,Point-to-Point Tunneling Protocol (PPTP) and generic routingencapsulation (GRE). Still, any of a variety of different tunnelingtechniques can be used.

Conventional techniques typically require that the mobile node 250 be inthe physical region covered by a particular foreign agent 215, 230 inorder for the handoff to occur. The processing and updating of relevantinformation that accompanies the handoff thus exacts a time delay beforethe mobile node 250 is able to begin communication with theinterconnection of networks 200 through the foreign agent of the regionin which the mobile node has newly arrived. During the time delay,moreover, any datagrams that arrive from a correspondent node will bedropped because of the temporary lack of a communication link with themobile node 250.

The present invention overcomes these problems. According to oneembodiment of the present invention illustrated in FIGS. 2A and 2B, thewireless node pair 202 includes a ghost-mobile node 220 in addition tothe mobile node 250. Although illustratively the ghost-mobile node 220is adjacent the mobile node 250, it is to be understood that theghost-mobile node can be a virtual node and need not reside at the samephysical location as the mobile node 250. The ghost-mobile node 220, forexample, can be set of software instructions running on a device that isremote from the mobile node 250 and that contains a transceiver forcommunicating with the mobile node.

Regardless of its physical embodiment, the ghost-mobile node 220operates by signaling a communication network node based upon apredicted future state of the mobile node 250. As illustrated in FIG.2A, the ghost-mobile node signals 220 an edge node that defines aforeign agent 215, 230. The foreign agent 215 communicatively links themobile node 250 to a communications network when the mobile node is in apredefined region served by the foreign agent. The ghost-mobile node220, however, signals the foreign agent before the mobile node arrivesin the predefined region based upon the prediction of the mobile node's250 future state.

The future state can be a physical state such as the location of themobile node 250, and the prediction can be the time that the mobile nodewill be in the predefined region served by the foreign agent 215.Accordingly, the predicted future state of the mobile node 250 canbased, for example, upon the trajectory of the mobile node or upon itsspeed. Alternately, the predicted future state of the mobile node 250can be based upon an estimated location of the mobile node.

According to one embodiment of the present invention, the mobile nodepair 202 can further include a Global Positioning System (GPS) unit tofacilitate the above-described predictions of the future state of themobile node 250. Using the GPS unit, location information on the mobilenode 250 can be obtained and subsequently used, for example, to estimatewhich of multiple foreign agents are closest and when the mobile node islikely to arrive in the region served by the closest foreign agent. Theghost-mobile node 220 can perform the function of determining theclosest foreign agent.

It be will readily appreciated, that other systems for determininglocation information can be used and that the present invention is notlimited to embodiments using GPS units. Any of various mobilecommunication techniques employed for mobile telephony can similarly beused, for example. Alternately, for example, the foreign agents 215, 230can be configured to triangulate the position of the mobile node 250using signal strength or through the use of wireless sensors. Thus, themobile node 250 can be configured to notify the foreign agents 215, 230of its position from time to time or at regular intervals.Alternatively, the foreign agents 215, 230 can be configured todetermine the location of the mobile node 250 from time to time or atregular intervals as the case may be.

By continuously and/or periodically determining its position via the GSPunit or other technique, the ghost-mobile node 220 can extrapolate fromthe current location and predict future locations of the mobile node250.

Any of a variety of different location prediction techniques can be usedby the ghost-mobile node 220. According to one embodiment of the presentinvention, a Kalman filter is used. The Kalman filter is describedgenerally, for example, in “An Introduction to the Kalman Filter”, byWelch G. and Bishop G., University of North Carolina TR 95-041, UNC,Chappell Hill, N.C. (2002). The Kalman filter can be implemented withinthe ghost-mobile node 220 to determine the amount of time before theghost-mobile node can send a registration message and act on behalf ofthe mobile node 250. The Kalman filter addresses the problem of tryingto estimate the state xε R^(n) of a discrete-time controlled processthat is governed by a linear stochastic difference equation. In general,the process is composed of a state vector (Equation 1, below) andmeasurement vectors (Equation 2, below).

The Kalman filter assumes that there is a state vector x such that:x _(k) =Ax _(k-1) +Bu _(k) +w _(k-1)   (1)with a measurement vector zε R^(n) such that:z _(k) =Hx _(k) +v _(k)   (2)The equations also include the values of w_(k) and v_(k), which arerandom variables representing the process noise of the measurement andstate vectors. The matrices A, B, and H relate the states and thedynamics of the system under study. In the context of a mobilecommunication protocol such as Mobile IP, the ghost-mobile node 220 cangive the velocity and position of the mobile node 250 at any given time.

The following equation (Equation 3) shows a relationship of the statevector and the basic dynamics of a mobile node with the well-knownrelationship of a 2-D object moving at constant speed. $\begin{matrix}{\begin{pmatrix}x \\y \\v_{x} \\v_{y}\end{pmatrix} = {{\begin{pmatrix}1 & 0 & t & 0 \\0 & 1 & 0 & t \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{pmatrix}\begin{pmatrix}x \\y \\v_{x} \\v_{y}\end{pmatrix}} + \begin{pmatrix}w_{x} \\w_{y} \\w_{x}^{s} \\w_{y}^{s}\end{pmatrix}}} & (3)\end{matrix}$

The measurement vector z_(k)=[xy]^(T) can be used in the recursivemechanics of the Kalman Filter. The filter uses an ongoing cycle wheretime-update equations determine the state ahead of time, and themeasurement update is used to adjust the internal parameters of thefilter. With these variables, the problem can be posed as a linearKalman Filter equation:X _(k) =AX _(k-1) +w _(k)   (4)Z _(k) =Hz _(k) +v _(k)   (5)where, $\begin{matrix}{A = {{\begin{pmatrix}1 & 0 & t & 0 \\0 & 1 & 0 & t \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{pmatrix}\text{:}\quad H} = {{\begin{pmatrix}1 & 0 & 0 & 0 \\0 & 1 & 0 & 0\end{pmatrix}\quad v_{k}} = {{\begin{pmatrix}v_{s} \\v_{y}\end{pmatrix}\quad w_{k}} = \begin{pmatrix}w_{x} \\w_{y} \\w_{x}^{s} \\w_{y}^{s}\end{pmatrix}}}}} & (6)\end{matrix}$

The time-update equations for the Kalman Filter are:x _(k) =Ax _(k-1) +Bu _(k) +w _(k-1)   (7)P _(k) =AP _(k-1) A ^(T) +Q   (8)In one scenario B=0 and P_(k) is the covariance matrix which isestimated from time step k-1 to step k. The matrix Q=E[w_(k)w_(k) ^(T)].

For measurement-update equations, the first equation (Equation 9, below)computes the Kalman gain, K_(k), the second equation (Equation 10,below) calculates the value of x_(k) which is used in Equation 7 tocompute the predicted value of the state vector. The third equation(Equation 11, below) updates the covariance matrix P_(k). The value ofthe co-variance matrix R=E[v_(k)v_(k) ^(T)] is needed and, in general,is the easier to determine since it is generally known how to measurethe position vector. Further, samples can be dedicated to determine theco-variance of v_(k).K _(k) =P _(k) ⁻ H ^(T)(HP _(k) ⁻ H ^(T) +R)⁻¹   (9)x _(k) =x _(k) ⁻ +K _(k)(z _(k) −Hx _(k) ⁻)   (10)P _(k)=(I−K _(k) H)P _(k) ⁻  (11)

Using an information processing tool, the values of the matrices R and Q(Equation 12) can be empirically determined to be for, example,$\begin{matrix}{Q = {{0.001*\begin{pmatrix}15 & 0 & 0 & 0 \\0 & 15 & 0 & 0 \\0 & 0 & 1 & 0 \\0 & 0 & 0 & 1\end{pmatrix}\quad R} = {0.000001*{\begin{pmatrix}100 & 0 \\0 & 0.001\end{pmatrix}.}}}} & (12)\end{matrix}$

The following is an example of an algorithm that can be used in theghost-mobile node to find a closest foreign agent using the measurementvector z_(k)=[xy]^(T):

-   -   g-MN (Home Address, HomeAgentAddress)        -   while (true) do            -   FA FindClosestFA(MN)            -   if distance (FA, MN) within threshold then                -   HFA FindHighestFA(FA, HomeAgentAddress) Register(FA,                    HomeAddress, HFA)            -   end

Those of ordinary skill in the art will readily recognize that othertechniques beside the Kalman filter can be used by the ghost-mobile node220 for location prediction. Other techniques for predicting a locationof the mobile node 250 include, for example, neural networks, linearprediction mechanisms, and modeling of stochastic processes.

Based upon the predicted future state of the mobile node 250, theghost-mobile node 220 can determine which foreign agent 210, 215, 230 islikely to serve as the mobile node's next communicative link. Forexample, a simple look-up database can be maintained by the networklisting each foreign agent and its location information. The locationcan be represented, for example, by a two-element vector, (x, y). Theghost-mobile node 220 can receive updated (x, y) information on thelocation. Using the updated information, the ghost-mobile node 220 cancalculate a distance to the closest foreign agent in the path of themobile node 250 based upon an estimated speed or trajectory of themobile node 250.

The ghost-mobile node 220 signals the network communications node thatdefines the mobile node's 250 next foreign agent 215, 230. Theghost-mobile node 220 signals the foreign agent 215, 230 ahead of themobile node's 250 arriving in the predefined region served by theforeign agent. The signal from the ghost-mobile node 220 can be aregistration request. The signal from the ghost-mobile node 220 cancause an allocation of communications network resources, the resourcesbeing those needed for relaying communications between thecommunications network and the mobile node. Indeed, the signal from theghost-mobile node 220 can elicit the same response from the networknodes defining the foreign agents 215, 230 as would be elicited were themobile node 250 physically present in the predefined region covered bythe particular foreign agent.

In the context of an IP-based network, the ghost-mobile node 220 cancreate “spoofed” Universal Datagram Packets (UDP) with the contents of alegitimate mobile node packet. The procedure can utilize raw sockets toconstruct the message, create all the registration and IP headers, andadd the authentication extensions using, for example, the MD5 checksumand a shared key.

As used herein, MD5 refers to an algorithm used to verify data integritythrough the creation of a 128-bit message digest from data input, whichmay be a message of any length. MD5 is intended for use with digitalsignature applications, which require that large files must becompressed by a secure method before being encrypted with a secret key,under a public key cryptosystem. MD5 is a standard based on the InternetEngineering Task Force (IETF) Request for Comments (RFC) 1321, which isfully incorporated herein by reference. Nonetheless, it will be readilyappreciated by those of ordinary skill in the art that other methods ofensuring data security can be used.

Many implementations of Mobile IP include protection againstregistration replay attacks by adding time-stamps and a “nonce,” arandom value sent in a communications protocol exchange and frequentlyused to detect replay attacks. Accordingly, the protocol is able to keepa consistent and secure Location Directory (LD). The nonce is aparameter that varies with time, but also can include a visit counter ona Web page or a special marker intended to limit or prevent theunauthorized replay or reproduction of a file. In any case, as theghost-mobile node 229 essentially forges registration packets on behalfof the mobile node 250, no time-stamping or nonce numbers need be used.As an alternative, a shared key authentication can be required betweenthe home agent, foreign agents, and the mobile node. Asymmetricauthentication as in a protocol such as 802.1X can be used as analternate to symmetric authentication for delegating authority to theghost-mobile node 220.

The signal from the ghost-mobile node 220 results in a preemptive setup,one that is effected before the mobile node 250 arrives in thepredefined area of coverage of the next foreign agent. The setup canentail all the aspects that occur in the beginning phase of a standardnetwork connection negotiation, including the negotiation of protocoldetails, communication rates, and error-handling approaches. These areneeded to allow the connection to proceed correctly and reliably, butabsent the participation of the ghost-mobile node 220 would have toawait the arrival of the mobile node 250 in the predefined regioncovered by the foreign agent 215, 230.

Accordingly, the ghost-mobile node 220 can increase the speed with whichhandoff occurs, thereby reducing setup delay and avoiding informationloses due to the dropping of datagram packets. The ghost-mobile node 220can replicate the registration request, handle the creation of tunnels,and replicate authentication and authorization information from themobile node 250, thus acting on behalf of the mobile node 250 before themobile node is in range of a next foreign agent 215, 230. Theghost-mobile node 220 also can buffer incoming traffic from acorrespondent host ring handoff to further insure against the loss ofinformation during a handoff. When the mobile node 250 leaves oneforeign agent 215 and moves into the vicinity of the next foreign agent230, registration will have already taken place and resources willalready have been allocated for connecting the mobile node to thecommunication network.

Referring still to FIGS. 2A and 2B, each of the network node pairs 204a, 204 b further includes ghost-foreign agents 225, 240 in addition tonetwork nodes defining foreign agents 215, 230. A ghost-foreign agent225, 240 transmits an advertisement notifying the mobile node 250 of theexistence of a next foreign agent 230, transmitting the advertisementfrom a foreign agent 215 currently connected with the mobile node 250.That is, the ghost-foreign agent 225 advertises a first foreign agent230 but does so using a second foreign agent 215. Thus, theadvertisement of foreign agent 230 by its ghost-foreign agent 225 isable to reach the mobile node 250 while the mobile node is in thepredefined region covered by foreign agent 215. Therefore, theghost-foreign agent 225 makes the mobile node aware of the foreign agent230 before it arrives in the predefined region covered by the foreignagent.

A foreign agent 210, 215, 230 typically includes in an advertisementmessage the vector of care-of addresses. As noted above, the vector ofcare-of addresses provide an IP address for each of the foreign agent'sancestors, as well as the foreign agent's own IP address. As a mobilenode 250 enters a predefined coverage region within the range ofcommunication of a foreign agent 215, the mobile node can submit aregistration request to the foreign agent, as described above. Theforeign agent 215, in turn, can initiate a registration request to theforeign agent 210, which can forward the registration request to thehome agent 205.

The home agent 205 can initiate a tunnel to the foreign agent 210 andtransmit a registration reply. The foreign agent 210 can create a tunnelto the foreign agent 215, defining a leaf foreign agent, and forward theregistration reply to the foreign agent. The foreign agent 215 then cantransmit the registration reply to the mobile node 250. According to oneembodiment of the present invention, the ghost-foreign agent 225 acts asan extension of a foreign agent 230 defining a leaf foreign agent.Accordingly, the ghost-foreign agent 225 is able to transmit theadvertisement of foreign agent 230 to the mobile node 250 as alreadydescribed above.

Referring now particularly to FIG. 2B, as the mobile node 250 leaves thefirst foreign agent 215 and moves toward the next foreign agent 230, theghost-mobile node 220 can send a registration request to the foreignagent 215. Accordingly, the foreign agent 215 can open a tunnel to thenext foreign agent 230 and send a registration reply. As the mobile node250 enters the communications range of the next foreign agent 230, andas the mobile node 250 has already received the advertisement from theghost-foreign agent 225, the mobile node 250 can send a registrationrequest to the next foreign agent. The mobile node 250 can then receivea registration reply as the ghost-mobile node 220 has already registeredand allocated resources for the mobile node 250.

FIG. 2C is a schematic diagram illustrating another exemplary networkarchitecture where foreign agent 280 is surrounded by foreign agents260, 265, 270, and 275. If mobility ratio is high, then foreign agent280 can create instances of a ghost-foreign agent corresponding toforeign agent 280 at foreign agent 260, 265, 270, and/or 275. Theseinstances can represent foreign agent 280 before the mobile nodeactually reaches the foreign agent within which it is disposed.

Each foreign agent 215, 230 creates ghost-foreign agent instances at thevicinity of other foreign agents. A ghost-foreign agent results in avirtual augmentation of the signal strength of a certain foreign agent,so that the signal strength appears to have increased and the coveragearea appears to have been augmented by a certain factor. Indeed, aghost-foreign agent appears to increase the amount of resourcesavailable for facilitating communication among interconnectedcommunication networks.

As already described, a basis of the proactive allocation ofcommunication resources for a stationary or moving mobile node is thevirtual instantiation of the ghost-mobile node in at least oneadditional wireless network node proximate to the predicted futurelocation of the mobile node. So, too, each foreign agent can create itsghost-foreign agent instances or virtual foreign agents aroundparticular thresholds. For example, if foreign agent coverage is denotedas r, a foreign agent can find all foreign agents within k*r, where k isa factor determined according to the expected mobility conditions of theforeign agent. Ghost-foreign agents can thus function as passiverepeaters of the operations of the corresponding foreign agent.

FIG. 3 is a schematic diagram illustrating a message structure assembledfor the home agent and/or foreign agent from the ghost-mobile node inaccordance with one embodiment of the inventive arrangements disclosedherein. The ghost-mobile node. includes as the IP source and IPdestinations the values of the original home agent's home address andthe home agent and/or foreign agent addresses respectively.

The home address and care-of-address are generally known, since thedecapsulation process takes place at the foreign agent. For example, thecare-of address matches the foreign agent address. The foreign agentaddress allows the content of the message to be forwarded to the mobilenode while the mobile node remains within the foreign network. Forhierarchical Mobile IP, the leaf foreign agent address is used as adestination for the registration message. Once the message has reachedthe foreign agent, the foreign agent forwards the registration packet toa higher foreign agent which forwards it to a still higher foreign agentor on to the home agent, depending upon the wired network infrastructureand the topology of foreign agents. This depends, for example, uponwhether the mobile node switches domains with no common foreign agents.

The present invention facilitates the use of any mobile node, whileallowing the code for the mobile node to remain unchanged. During theabsence of a ghost-mobile node, the mobile node can rely upon reactivemechanisms of the communications protocol in use, whether Mobile IP oranother mobile communications protocol. In general, a ghost-mobile nodecan locate the closest foreign agent in the vicinity of the mobile node.If the distance is within a given threshold, then the highest foreignagent within the hierarchy, that is the home foreign agent, can belocated and the mobile node can be registered with that home foreignagent.

FIG. 4 is a schematic diagram illustrating a data packet that can beformulated and sent by the ghost-foreign agent in accordance with oneembodiment of the inventive arrangements disclosed herein. Theghost-foreign agent determines all the foreign agents within a ratio(threshold) and creates a packet, for example an Internet ControlMessage Protocol (ICMP), with the information as shown in FIG. 4. Thecare-of-addresses are already a persistent part of the foreign agentconfiguration file and sequence numbers can be spoofed. Additionally,the ghost-foreign agent should assemble the raw socket using the foreignagent address as a source with a broadcast address as destination.

FIG. 5 provides a flowchart of steps illustrative of a method aspect ofthe invention. The method 500 includes in step 510 predicting a futurephysical state of the mobile node. In step 520, the method 500 includessignaling the foreign agent based upon the predicted future state of themobile node. The method 500 optionally includes in step 530 bufferingcommunications communicated to the mobile node from a correspondent nodeof the communications network.

Optionally, the method 500 further includes in step 540 advertising theforeign agent so that the mobile node is aware of the foreign agent whenthe mobile node is located outside the predefined region. In step 550,the method 500 also optionally includes estimating which next foreignagent is closest to the mobile node.

The present invention can be realized in hardware, software, or acombination of hardware and software. The present invention can berealized in a centralized fashion in one computer system, or in adistributed fashion where different elements are spread across severalinterconnected computer systems. Any kind of computer system or otherapparatus adapted for carrying out the methods described herein issuited. A typical combination of hardware and software can be a generalpurpose computer system with a computer program that, when being loadedand executed, controls the computer system such that it carries out themethods described herein.

The present invention also can be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

This invention can be embodied in other forms without departing from thespirit or essential attributes thereof. Accordingly, reference should bemade to the following claims, rather than to the foregoingspecification, as indicating the scope of the invention.

1. A system for communication between a mobile node and a communicationsnetwork, the communications network having at least one communicationsnetwork node that defines a foreign agent and that communicates with themobile node in a predefined region, the system comprising: aghost-foreign agent for advertising the foreign agent so that the mobilenode is aware of the foreign agent when the mobile node is locatedoutside the predefined region; and a ghost-mobile node for signaling theforeign agent based upon a predicted future state of the mobile node. 2.The system as defined in claim 1, wherein signaling includes registeringthe mobile node with the foreign agent.
 3. The system as defined inclaim 1, wherein signaling includes causing the communications networkto allocate communications network resources to relaying communicationsbetween the communications network and the mobile node.
 4. The system asdefined in claim 1, wherein the predicted future state is based upon atleast one of a trajectory of the mobile node, a speed of the mobilenode, and an estimated location of the mobile node.
 5. The system asdefined in claim 1, wherein the ghost-foreign agent is responsive to atleast one of instructions from the foreign agent and a predeterminedthreshold.
 6. The system as defined in claim 1, wherein the ghost-mobilenode buffers communications communicated to the mobile node from acorrespondent node of the communications network.
 7. A wireless nodepair comprising: a mobile node for communicating with a communicationsnetwork having at least communications network node; and a ghost-mobilenode for signaling the at least one communications network node basedupon a predicted future state of the mobile node.
 8. The wireless nodepair as defined in claim 7, wherein the signaling comprises registeringthe mobile node with the at least one communications network node. 9.The wireless node pair as defined in claim 7, wherein the signalingcauses the communications network to allocate communications networkresources to relaying communications between the communications networkand the mobile node.
 10. The wireless node pair as defined in claim 7,wherein the predicted future state is based upon at least one of atrajectory of the mobile node, a speed of the mobile node, and anestimated location of the mobile node.
 11. The wireless node pair asdefined in claim 7, wherein the ghost-mobile node buffers communicationscommunicated to the mobile node from a correspondent node of thecommunications network.
 12. The wireless node pair as defined in claim7, wherein the predicted future state is predicted by the ghost-mobilenode.
 13. The wireless node pair as defined in claim 7, wherein the atleast one network communications node comprises a plurality of networkcommunications nodes, and wherein ghost-mobile node determines a closestcommunications network node from among the plurality of communicationsnetwork nodes.
 14. A network node pair comprising: a foreign agent forrelaying communications between a communications network and a mobilenode when the mobile node is located in a predefined region; and aghost-foreign agent for advertising the foreign agent so that the mobilenode is notified of the foreign agent's presence in the communicationsnetwork when the mobile node is located outside the predefined region.15. The network node pair as defined in claim 14, wherein theghost-foreign agent is response to instructions from the foreign agent.16. The network node pair as defined in claim 14, wherein theghost-foreign agent is responsive to a predetermined threshold.
 17. Amethod of wireless communication between a mobile node and acommunications network, the communications network having at least onecommunications network node that defines a foreign agent and thatcommunicates with the mobile node in a predefined region, the methodcomprising the steps of:. predicting a future physical state of themobile node; and signaling the foreign agent based upon the predictedfuture state of the mobile node.
 18. The method as defined in claim 17,wherein the step of predicting is based upon at least one of atrajectory of the mobile node, a speed of the mobile node, and anestimated location of the mobile node.
 19. The method as defined inclaim 17, wherein the step of signaling comprises registering the mobilenode with the foreign agent.
 20. The method as defined in claim 17,wherein the step of signaling causes the communications network toallocate communications network resources to relaying communicationsbetween the communications network and the mobile node.
 21. The methodas defined in claim 17, further comprising the step of bufferingcommunications communicated to the mobile node from a correspondent nodeof the communications network.
 22. The method as defined in claim 17,wherein the at least one communications network node comprises a pair ofnetwork communication nodes defining a first and a second foreign agent,and further comprising estimating which foreign agent is closest to themobile node.
 23. The method as defined in claim 17, further comprisingthe step of advertising the foreign agent so that the mobile node isaware of the foreign agent when the mobile node is located outside thepredefined region.
 24. The method as defined in claim 23, wherein the atleast one communications network node comprises a pair of networkcommunication nodes defining a first and a second foreign agent, andwherein the step of advertising comprises advertising the second foreignagent using the first foreign agent.
 25. A computer readable storagemedium for use with communications network having at least onecommunications network node that defines a foreign agent and thatcommunicates with the mobile node in a predefined region, the storagemedium comprising computer instructions for: predicting a futurephysical state of the mobile node; and signaling the foreign agent basedupon the predicted future state of the mobile node.
 26. The computerreadable storage medium as defined in claim 25, wherein the at least onecommunications network node comprises a pair of network communicationnodes defining a first and a second foreign agent, and furthercomprising computer instructions for estimating which foreign agent isclosest to the mobile node.
 27. The computer readable storage medium asdefined in claim 25, further comprising computer instructions foradvertising the foreign agent so that the mobile node is aware of theforeign agent when the mobile node is located outside the predefinedregion
 28. The computer readable storage medium as defined in claim 27,wherein the at least one communications network node comprises a pair ofnetwork communication nodes defining a first and a second foreign agent,and wherein the computer instruction for advertising comprises acomputer instruction for advertising the second foreign agent using thefirst foreign agent.